I have the Zagg Keyboard folio case for the iPad Air, just love it and for 2 reasons it has a dedicated row of keys for the controls for the Air I found that other brands have those commands as additions to the number keys and I didn't want to have to use control or FN to get to those controls. Plus it has the lighted keyboard which is great for using the iPad at night or low light conditions.
It doesn't add too much extra weight to the Air but then I was willing to give up the lightness for having the keyboard.